Dressing apparatus and polishing apparatus

ABSTRACT

A dressing apparatus dresses a polishing surface of a polishing table used for polishing a workpiece such as a semiconductor wafer in a polishing apparatus. The dressing apparatus comprises a dresser having an elongate dressing surface for dressing the polishing surface, and the dressing surface has a flat surface which contacts the polishing surface, and one of a tapered surface extending from the flat surface and inclined so as to be away from the polishing surface and a curved surface extending from the flat surface and curved so as to be away from the polishing surface.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a dressing apparatus for dressing a polishing surface of a polishing table used for polishing a workpiece such as a semiconductor wafer in a polishing apparatus, and a polishing apparatus having such dressing apparatus for polishing a workpiece such as a semiconductor wafer to a flat mirror finish.

[0003] 2. Description of the Related Art

[0004] Recently, semiconductor devices have become more integrated, and structure of semiconductor elements has become more complicated. In addition, as the number of layers in multilayer interconnections used for a logical system has been increased, irregularities of the surface of the semiconductor device are increased, so that the step height on the surface of the semiconductor device becomes larger. This is because in manufacturing semiconductor devices, a process forming a thin film is performed and a micromachining process such as patterning or formation of holes is performed, and then a process for forming a subsequent film is performed, and such processes are repeated many times.

[0005] When the irregularities of the surface of the semiconductor device are increased, the following problems arise. The thickness of a film formed in a portion having a step is relatively small. An open circuit is caused by disconnection of interconnections, or a short circuit is caused by insufficient insulation between the layers. As a result, good products cannot be obtained, and the yield is reduced. Further, even if a semiconductor device initially works normally, reliability of the semiconductor device is lowered after a long-term use.

[0006] Another problem is caused in a lithography process by the irregularities of the surface of the semiconductor device. Specifically, at the time of exposure in the lithography process, if the irradiation surface has irregularities, then a lens unit in an exposure system is locally unfocused. Therefore, if the irregularities of the surface of the semiconductor device are increased, then it is difficult to form a fine pattern on the semiconductor device.

[0007] Thus, in the manufacturing process of a semiconductor device, it is increasingly important to planarize the surface of the semiconductor device. The most important one of the planarizing technologies is chemical mechanical polishing (CMP). In the chemical mechanical polishing in which a polishing apparatus is used, while a polishing liquid containing abrasive particles such as silica (SiO₂) therein is supplied onto a polishing surface such as a polishing pad, a substrate such a semiconductor wafer is brought into sliding contact with the polishing surface, thereby polishing a surface of the substrate.

[0008] Conventionally, as shown in FIG. 17, such a polishing apparatus has a polishing table 102 having a polishing cloth (polishing pad) 100 attached to the upper surface thereof, and a top ring 104 for holding a substrate W such as a semiconductor wafer and pressing the substrate W against the polishing cloth 100 on the polishing table 102. A polishing liquid containing abrasive particles is supplied from a nozzle 106 onto the polishing cloth 100 and retained on the polishing cloth 100. The polishing cloth 100 on the polishing table 102 constitutes a polishing surface. During operation, the top ring 104 exerts a certain pressure, and the surface of the substrate W held against the polishing surface of the polishing table 102 is therefore polished to a flat mirror finish while the top ring 104 and the polishing table 102 are rotating. The polishing liquid comprises abrasive particles such as silica particles, and chemical solution such as alkali solution in which the abrasive particles are suspended. Thus, the substrate W is chemically and mechanically polished by a combination of a mechanical polishing action of abrasive particles in the polishing liquid and a chemical polishing action of chemical solution in the polishing liquid.

[0009] When the polishing process is finished, the polishing capability of the polishing cloth 100 is gradually deteriorated due to a deposition of the abrasive particles and ground-off particles removed from the substrate, and due to changes in the characteristics of the surface of the polishing cloth. Therefore, if the same polishing cloth is used to repeatedly polish the substrates W, the polishing rate of the polishing apparatus is lowered, and the polished substrates tend to suffer polishing irregularities. Therefore, it has been customary to condition the polishing cloth according to a process called “dressing” for recovering the surface of the polishing cloth before, or after, or during polishing.

[0010] In order to dress the surface of the polishing cloth 100 which has been deteriorated by polishing, a dressing apparatus 108 having a dressing surface is provided adjacent to the polishing table 102. In operation, the dressing surface of the dressing apparatus 108 is pressed against the polishing surface of the polishing table 102, and the dressing surface and the polishing table 102 are rotated relatively to each other for thereby bringing the dressing surface in sliding contact with the polishing surface. Thus, the polishing liquid and the ground-off particles attached to the polishing surface are removed, and planalization and regeneration of the polishing surface are conducted.

[0011] In order to primarily remove the polishing liquid and the ground-off particles from the polishing surface, the dressing apparatus 108 having a dressing surface composed of a nylon brush is mainly used. In order to primarily planalize the polishing surface by scraping off the polishing surface slightly, the dressing apparatus 108 having a diamond dresser is mainly used. The uniformity of the polishing surface which has been dressed affects greatly polishing precision of the workpiece (substrate).

[0012] However, the above-mentioned polishing apparatus has the following problems:

[0013] The first problem is that in case of polishing a substrate by a polishing table which rotates on its own axis, there is no relative movement between the polishing surface and the substrate on the rotation center of the polishing table, and hence the substrate is polished on an area of the polishing surface away from the rotation center of the polishing table. Therefore, the diameter of the polishing table 102 should be at least two times the diameter of the substrate W. Thus, the size of the polishing apparatus becomes large, and a large installation space of the polishing apparatus is required and the cost of facilities is high. This drawback is becoming significant with increasing diameter of the substrate W.

[0014] The second problem is presented by the polishing cloth 100 made of material having elasticity such as urethane. In general, a device pattern on the upper surface of the semiconductor wafer (substrate) W has various irregularities having various dimensions and steps, and is composed of different material. When the semiconductor wafer W having step-like irregularities is planarized by the polishing cloth 100 having elasticity, not only raised regions but also depressed regions are polished, and hence a large amount of material is removed from the semiconductor wafer and a long period of time is required until the semiconductor wafer is planarized. Thus, the operation cost in the polishing process is increased and irregularities of the polished surface of the semiconductor wafer are difficult to be eliminated, with the result that a high flatness of the polished surface cannot be obtained. Further, regions on which microscopic irregularities are concentrated are polished at a high polishing rate, and regions on which macroscopic irregularities exist are polished at a low polishing rate. Thus, a large undulation is formed on the polished surface of the semiconductor wafer.

[0015] The third problem is presented by operating cost in the polishing process and environmental pollution. In order to polish the semiconductor wafer to a high degree of flatness, a polishing liquid needs to be supplied abundantly onto the polishing cloth 100. However, the supplied polishing liquid is discharged from the polishing cloth 100 at a high rate without being used in an actual polishing process. This leads to a high operating cost in the polishing process because the polishing liquid is expensive. Further, since the polishing liquid contains a large amount of abrasive particles such as silica particles, and may contain chemicals such as acids or alkalis to thus form slurry-like material, it is necessary to treat waste liquid discharged from the polishing process for thereby preventing environmental pollution. This also leads to a high operating cost in the polishing process.

[0016] In order to solve the first problem, it is conceivable that the polishing apparatus incorporates the polishing table 102 which makes a circulative translational motion (scroll motion) along a circle having a certain radius. In this case, every point on the polishing surface of the polishing table makes the same motion, and hence the diameter of the polishing surface on the polishing table may be equal to the dimension obtained by adding two times radius of gyration of the polishing table 102 to the diameter of the semiconductor wafer (substrate).

[0017] Thus, the polishing apparatus may be small in size and the installation space of the polishing apparatus may be reduced to lower the overall cost including manufacturing cost of the polishing apparatus, operating cost in the plant and cost of equipment.

[0018] In order to solve the second and third problems, it is conceivable to polish the semiconductor wafers (substrates) by the use of an abrading plate. The abrading plate comprises abrasive particles such as silica particles and a binder for binding the abrasive particles, and is formed into a flat plate. The abrading plate may be called a fixed abrasive. The abrading plate is attached to the upper surface of the polishing table, and the semiconductor wafer W held by the top ring 104 is pressed against the abrading plate under a certain pressure and brought in sliding contact with the abrading plate. With the sliding contact between the abrading plate and the semiconductor wafer, the semiconductor wafer is polished while the binder is broken or dissolved to thus generate fresh freed abrasive particles.

[0019] According to the above polishing process, the abrading plate is harder than the polishing cloth and has less elastic deformation than the polishing cloth, and hence only the raised regions on the semiconductor wafer are polished and undulation of the polished surface of the semiconductor wafer is prevented from being formed. Further, since a slurry-like polishing liquid containing a large amount of abrasive particles is not used, the amount of wastes discharged from the polishing process and required to be treated is greatly reduced, and hence the operating cost is reduced and environmental protection is easily carried out. Since the polishing liquid containing abrasive particles is not used, equipment for supplying the polishing liquid is not required.

[0020] In the case where the abrading plate is attached to the polishing table which makes a circulative translational motion (scroll motion) and the substrate is polished by the abrading plate, the polishing surface of the abrading plate includes a central region which is always brought in contact with the substrate, a peripheral region which is always brought out of contact with the substrate, and an intermediate region which is brought in contact or out of contact with the abrading plate. As a result, as shown in FIG. 18, the surface of the abrading plate 110, i.e., the polishing surface 110 a has a depressed region. That is, the central region A of the polishing surface suffers a large abrasion loss, the peripheral region C suffers hardly any abrasion loss, and the intermediate region B suffers an inclined abrasion loss. Even if the substrate (semiconductor wafer) continues to be polished by the polishing surface shown in FIG. 18, the substrate cannot be planarized. Thus, it is necessary to dress the polishing surface of the abrading plate.

[0021] In such a case, if dressing of the polishing surface is conducted by a dressing tool having a circular dressing surface or an annular dressing surface smaller than the polishing surface as in the case of conventional dressing process, then the polishing surface of the abrading plate having irregularities is locally dressed, and hence it is difficult to planarize the entire area of the polishing surface. These circumstances hold true for the dressing process of the polishing surface composed of the polishing cloth attached to the polishing table which makes a circulative translational motion (scroll motion).

SUMMARY OF THE INVENTION

[0022] It is therefore an object of the present invention to provide a dressing apparatus which can easily and reliably planarize a polishing surface, having irregularities, on a polishing table and regenerate the polishing surface efficiently.

[0023] Another object is to provide a dressing apparatus which can dress a polishing surface of a polishing table, which makes a circulative translational motion (scroll motion or circulative orbital motion) and has an advantage of a small installation space, by a dresser which requires a small installation space, and can increase a processing capability of the polishing table per unit installation area.

[0024] According to a first aspect of the present invention, there is provided a dressing apparatus for dressing a polishing surface of a polishing table for polishing a surface of a workpiece, the dressing apparatus comprising: a dresser having an elongate dressing surface for dressing the polishing surface, the dressing surface having a flat surface which contacts the polishing surface, and one of a tapered surface extending from the flat surface and inclined so as to be away from the polishing surface and a curved surface extending from the flat surface and curved so as to be away from the polishing surface.

[0025] According to a second aspect of the present invention, there is provided a dressing apparatus for dressing a polishing surface of a polishing table for polishing a surface of a workpiece, the dressing apparatus comprising: a dresser having an elongate dressing surface for dressing the polishing surface, the dressing surface comprising a circular arc surface.

[0026] According to the first and second aspects of the present invention, because the boundary portion between a contact portion and a noncontact portion of the dressing surface and the polishing surface has a smooth shape, a stick-slip caused between the dressing surface and the polishing surface can be decreased, and the dresser can be smoothly moved. Thus, generation of vibration of the dresser can be suppressed.

[0027] According to the present invention, the size of the dressing surface in the long side has the dimension larger than that of the moving area of the polishing surface of the polishing table, and the dresser is movable along the polishing surface by a horizontally moving mechanism. Thus, the entire area of the polishing surface can be dressed by bringing the dressing surface in contact with the polishing surface and moving the dressing surface. Therefore, even if the polishing surface has irregularities locally, the entire area of the polishing surface can be reliably planalized, and the polishing surface can be efficiently and uniformly regenerated.

[0028] Further, the size of the dresser in the long side must have the dimension equal to or larger than that of the moving area of the polishing table, i.e. the dimension obtained by adding a scroll diameter to a diameter of the polishing table. However, the size of the dresser in the short side may be as small as possible, provided that the dressing condition permits. Thus, the rectangular dresser can save an installation space, compared with the circular dresser.

[0029] The horizontally moving mechanism may comprise a translation mechanism for causing the dresser to perform a translation along the polishing surface at the constant velocity. With this structure, relative vectors on contact surface between the dressing surface and the polishing surface which makes a scroll motion are equalized over the entire polishing surface, and contact time between the dressing surface and the polishing surface is equalized over the entire polishing surface, and hence uniform dressing can be performed.

[0030] According to a third aspect of the present invention, there is provided a dressing apparatus for dressing a polishing surface of a polishing table for polishing a surface of a workpiece, the dressing apparatus comprising: a dresser having a dressing surface for dressing the polishing surface; and a controller for controlling a pressing force for pressing the dresser against the polishing surface; wherein when a contact area between the dressing surface of the dresser and the polishing surface is changed by relative movement of the dresser and the polishing table during dressing, the pressure force is changed according to the contact area by the controller.

[0031] According to the present invention, in the case where a contact area between the dressing surface and the polishing surface is changed by relative movement between the dresser and the polishing table during dressing, a pressing force of the dresser applied to the polishing table (pressing force applied to the entire dressing surface) is changed according to the contact area by the controller, and hence a pressing force for pressing the dressing surface against the polishing surface (pressure applied to the polishing surface per unit area) can be equalized over the entire polishing surface. Thus, an amount of a material removed from the polishing surface on the polishing table can be uniformized over the entire polishing surface.

[0032] According to a fourth aspect of the present invention, there is provided a dressing apparatus for dressing a polishing surface of a polishing table for polishing a surface of a workpiece, the dressing apparatus comprising: a dresser having a dressing surface for dressing the polishing surface, the dressing surface having a flat surface which contacts the polishing surface, and one of a tapered surface extending from the flat surface and inclined so as to be away from the polishing surface and a curved surface extending from the flat surface and curved so as to be away from the polishing surface; wherein the dresser performs no rotational motion about its own axis during dressing.

[0033] According to a fifth aspect of the present invention, there is provided a dressing apparatus for dressing a polishing surface of a polishing table for polishing a surface of a workpiece, the dressing apparatus comprising: a dresser having a dressing surface for dressing the polishing surface, the dressing surface comprising a circular arc surface; wherein the dresser performs no rotational motion about its own axis during dressing.

[0034] In a preferred aspect of the present invention, a dresser cleaning container is provided to clean the dressing surface of the dresser. If the dresser cleaning container is formed into an elongate shape so as to correspond to the shape of the rectangular dresser, the dresser cleaning container can save its installation space. Further, foreign matter attached to the dressing surface or fragments of the dresser element such as diamond particles are removed from the dresser, thus eliminating harmful influence caused by them on the polishing surface.

[0035] According to a sixth aspect of the present invention, there is provided a polishing apparatus for polishing a surface of a workpiece, the polishing apparatus comprising: a polishing table having a polishing surface; and a dresser having a dressing surface for dressing the polishing surface, the dresser being movable along the polishing surface by a moving mechanism; wherein a shape of the polishing surface is arranged such that a contact area between the dressing surface of the dresser and the polishing surface is not changed when the dresser is moved by the moving mechanism.

[0036] According to the present invention, a contact area between the dressing surface of the dresser and the polishing surface is not changed over the entire area where the dresser moves. Thus, a pressing force for pressing the dresser against the polishing surface can be constant, irrespective of the position of the dresser. The shape and size of the polishing surface are set such that the polishing surface is contained in a locus described by the outer periphery of the dresser. As an example of the shape of the polishing surface, the polishing surface is substantially rectangular, and a dimension of at least one side of the substantially rectangular polishing surface is shorter than a dimension of the dresser in the long side, and the moving direction of the dresser is perpendicular to the one side of the polishing surface and the moving distance of the dresser is shorter than a dimension of another side of the polishing surface.

[0037] According to a seventh aspect of the present invention, there is provided a polishing apparatus for polishing a surface of a workpiece, comprising: a polishing table having a polishing surface; a workpiece holder for holding a workpiece; a pressing device for pressing the workpiece held by the workpiece holder against the polishing surface; and a dressing apparatus for dressing the polishing surface, the dressing apparatus comprising the dresser of the above first through fifth aspects of the present invention.

[0038] The above and other objects, features, and advantages of the present invention will be apparent from the following description when taken in conjunction with the accompanying drawings which illustrates preferred embodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039]FIG. 1 is a plan view showing a layout of various components of a polishing apparatus according to an embodiment of the present invention;

[0040]FIG. 2 is an elevational view showing the polishing apparatus shown in FIG. 1;

[0041]FIG. 3 is a perspective view showing a polishing table and a dressing apparatus according to an embodiment of the present invention;

[0042]FIG. 4 is a vertical cross-sectional view of the polishing table;

[0043]FIG. 5A is a cross-sectional view taken along line P-P of FIG. 4;

[0044]FIG. 5B is a cross-sectional view taken along line X-X of FIG. 5A;

[0045]FIG. 6 is a plan view of the dressing apparatus shown in FIG. 3;

[0046]FIG. 7 is a schematic view showing a configuration of cross section of an elongate (bar-like) dresser;

[0047]FIG. 8 is a schematic view showing a configuration of cross section of an elongate (bar-like) dresser;

[0048]FIG. 9 is a front view with a partially cross-sectioned part of the dressing apparatus shown in FIG. 6;

[0049]FIG. 10 is a left side view with a partially cross-sectioned part of the dressing apparatus shown in FIG. 6;

[0050]FIG. 11 is a schematic view showing the manner in which a pressing force of a dresser is controlled in the dressing apparatus;

[0051]FIG. 12A is a schematic view showing the manner in which a pressing force for pressing a dressing surface against a polishing surface is controlled using the method for controlling the pressing force of the dresser shown in FIG. 11, and specifically showing the relationship between the polishing table and the dresser;

[0052]FIG. 12B is a graph showing the relationship between the distance from a center of the polishing table, and a pressing force and a pressure of the dresser shown in FIG. 12A;

[0053]FIG. 13 is a plan view of a polishing table according to another embodiment of the present invention;

[0054]FIG. 14A is a plan view of a linear polishing apparatus according to another embodiment of the present invention;

[0055]FIG. 14B is a front view of the linear polishing apparatus according to another embodiment of the present invention;

[0056]FIG. 15 is a perspective view of the linear polishing apparatus shown in FIG. 14;

[0057]FIG. 16A is a plan view showing a dressing apparatus and a polishing apparatus having such dressing apparatus according to still another embodiment of the present invention;

[0058]FIG. 16B is a side view showing the dressing apparatus and the polishing apparatus having such dressing apparatus according to still another embodiment of the present invention;

[0059]FIG. 17 is a schematic cross-sectional view of a conventional polishing apparatus; and

[0060]FIG. 18 is a schematic cross-sectional view showing the state of a polishing surface in the conventional polishing apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] Next, a dressing apparatus and a polishing apparatus having such dressing apparatus according embodiments of the present invention will be described below with reference to drawings.

[0062]FIG. 1 is a plan view showing a layout of various components of a polishing apparatus according to an embodiment of the present invention. FIG. 2 is an elevational view showing the polishing apparatus shown in FIG. 1. As shown in FIG. 1, a polishing apparatus according to the present invention comprises four load-unload stages each for placing a wafer cassette 1 which accommodates a plurality of semiconductor wafers. The load-unload stage 2 may have a mechanism for raising and lowering the wafer cassette 1. A transfer robot 4 having two hands is provided on rails 3 so that the transfer robot 4 can move along the rails 3 and access the respective wafer cassettes 1 on the respective load-unload stages 2.

[0063] Two cleaning apparatuses 5 and 6 are disposed at the opposite side of the wafer cassettes 1 with respect to the rails 3 of the transfer robot 4. The cleaning apparatuses 5 and 6 are disposed at positions that can be accessed by the hands of the transfer robot 4. Between the two cleaning apparatuses 5 and 6 and at a position that can be accessed by the transfer robot 4, there is provided a wafer station 48 having four wafer supports 7, 8, 9 and 10. The cleaning apparatuses 5 and 6 have a spin-dry mechanism for drying a semiconductor wafer by spinning the semiconductor wafer at a high speed, and hence the two-stage cleaning or three-stage cleaning of the semiconductor wafer can be conducted without replacing any cleaning module.

[0064] An area B in which the cleaning apparatuses 5 and 6 and the wafer station 48 having the wafer supports 7, 8, 9 and 10 are disposed and an area A in which the wafer cassettes 1 and the transfer robot 4 are disposed are partitioned by a partition wall 14 so that the cleanliness of the area B and the area A can be separated. The partition wall 14 has an opening for allowing semiconductor wafers to pass therethrough, and a shutter 11 is provided at the opening of the partition wall 14. A transfer robot 20 having two hands is disposed at a position where the transfer robot 20 can access the cleaning apparatus 5 and the three wafer supports 7, 9 and 10, and a transfer robot 21 having two hands is disposed at a position where the transfer robot 21 can access the cleaning apparatus 6 and the three wafer supports 8, 9 and 10.

[0065] The wafer support 7 is used to transfer a semiconductor wafer between the transfer robot 4 and the transfer robot 20. The wafer support 8 is used to transfer a semiconductor wafer between the transfer robot 4 and the transfer robot 21. The wafer support 9 is used to transfer a semiconductor wafer from the transfer robot 21 to the transfer robot 20. The wafer support 10 is used to transfer a semiconductor wafer from the transfer robot 20 to the transfer robot 21.

[0066] A cleaning apparatus 22 is disposed at a position adjacent to the cleaning apparatus 5 and accessible by the hands of the transfer robot 20, and another cleaning apparatus 23 is disposed at a position adjacent to the cleaning apparatus 6 and accessible by the hands of the transfer robot 21.

[0067] All the cleaning apparatuses 5, 6, 22 and 23, the wafer supports 7, 8, 9 and 10 of the wafer station 48, and the transfer robots 20 and 21 are placed in the area B. The pressure in the area B is adjusted so as to be lower than the pressure in the area A. Each of the cleaning apparatuses 22 and 23 is capable of cleaning both surfaces of a semiconductor wafer.

[0068] The polishing apparatus shown in FIG. 1 has a housing 46 for enclosing various components therein. The housing 46 constitutes an enclosing structure. The interior of the housing 46 is partitioned into a plurality of compartments or chambers (including the areas A and B) by partitions 14, 15, 16, 24 and 47.

[0069] A polishing chamber separated from the area B by the partition wall 24 is formed, and is further divided into two areas C and D by the partition wall 47. In each of the two areas C and D, there are provided a polishing table 34 which makes a rotating motion and a polishing table 35 which makes a scroll motion. Further, in each of the two areas C and D, there are provided a top ring 32 for holding a semiconductor wafer and pressing the semiconductor wafer against the polishing tables 34, 35, a polishing liquid nozzle 40 for supplying a polishing liquid to the polishing table 34, a dresser 38 for dressing the polishing table 34, and a dressing apparatus 50 for dressing the polishing table 35.

[0070]FIG. 2 shows the relationship between the top ring 32 and the polishing tables 34 and 35. As shown in FIG. 2, the top ring 32 is supported from a top ring head 31 by a top ring drive shaft 91 which is rotatable. The top ring head 31 is supported by a support shaft 92 which can be angularly positioned, and the top ring 32 can access the polishing tables 34 and 35 and a rotary transporter 27 (described later on). The dresser 38 is supported from a dresser head 94 by a dresser drive shaft 93 which is rotatable. The dresser head 94 is supported by an angularly positionable support shaft 95 for moving the dresser 38 between a standby position and a dressing position over the polishing table 34. The polishing table 34 and the dresser 38 are such a type as to be rotatable about their own axes.

[0071] As shown in FIG. 1, the dressing apparatus 50 for dressing the polishing table 35 comprises an elongate dresser 51 for dressing a polishing surface on the polishing table 35 by translational motion along the surface of the polishing table 35 which makes a scroll motion, and a dresser cleaning container 54 for cleaning the dresser 51.

[0072] As shown in FIG. 1, in the area C separated from the area B by the partition wall 24 and at a position that can be accessed by the hands of the transfer robot 20, there is provided a reversing device 28 for reversing a semiconductor wafer, and at a position that can be accessed by the hands of the transfer robot 21, there is provided a reversing device 28′ for reversing a semiconductor wafer. The partition wall 24 between the area B and the areas C, D has two openings each for allowing semiconductor wafers to pass therethrough, one of which is used for transferring the semiconductor wafer to or from the reversing device 28 and the other of which is used for transferring the semiconductor wafer to or from the reversing device 28′. Shutters 25 and 26 are provided at the respective openings of the partition wall 24.

[0073] A rotary transporter 27 is disposed below the reversing devices 28 and 28′ and the top rings 32, for transferring semiconductor wafers between the cleaning chamber (area B) and the polishing chamber (areas C and D). The rotary transporter 27 has four stages for placing a semiconductor wafer at equal angular intervals, and can hold a plurality of semiconductor wafers thereon at the same time. The semiconductor wafer which has been transported to the reversing device 28 or 28′ is transferred to the rotary transporter 27 by actuating a lifter 29 or 29′ disposed below the rotary transporter 27 when the center of the stage of the rotary transporter 27 is aligned with the center of the semiconductor wafer held by the reversing device 28 or 28′. The semiconductor wafer placed on the stage of the rotary transporter 27 is transported to a position below one of the top rings 32 by rotating the rotary transporter 27 by an angle of 90° . At this time, the top ring 32 is positioned above the rotary transporter 27 beforehand by a swing motion thereof. The semiconductor wafer is transferred from the rotary transporter 27 to the top ring 32 by actuating a pusher 30 or 30′ disposed below the rotary transporter 27 when the center of the top ring 32 is aligned with the center of the semiconductor wafer placed on the stage of the rotary transporter 27.

[0074] The semiconductor wafer transferred to the top ring 32 is held under vacuum by a vacuum attraction mechanism of the top ring 32, and transported to the polishing table 34. Thereafter, the semiconductor wafer is polished by a polishing surface comprising a polishing cloth or a grinding stone (or a fixed abrasive) attached on the polishing table 34. The second polishing tables 35 which makes a scroll motion is disposed at a position that can be accessed by the top ring 32. With this arrangement, a primary polishing of the semiconductor wafer can be conducted by the first polishing table 34, and then a secondary polishing of the semiconductor wafer can be conducted by the second polishing table 35. Alternatively, depending on a kind of a film on the semiconductor wafer, the primary polishing of the semiconductor wafer can be conducted by the second polishing table 35, and then the secondary polishing of the semiconductor wafer can be conducted by the first polishing table 34. In this case, since the second polishing table 35 has a smaller-diameter polishing surface than the first polishing table 34, a grinding stone (or a fixed abrasive) which is more expensive than a polishing cloth is attached to the second polishing table 35 to thereby conduct a primary polishing of the semiconductor wafer. On the other hand, the polishing cloth having a shorter life but being cheaper than the grinding stone (or the fixed abrasive) is attached to the first polishing table 34 to thereby conduct a finish polishing of the semiconductor wafer. This arrangement or utilization may reduce the running cost of the polishing apparatus. If the polishing cloth is attached to the first polishing table and the grinding stone (or fixed abrasive) is attached to the second polishing table, then the polishing table system may be provided at a lower cost. This is because the grinding stone (or the fixed abrasive) is more expensive than the polishing cloth, and the price of the grinding stone (or the fixed abrasive) is substantially proportional to the diameter of the grinding stone. Further, since the polishing cloth has a shorter life than the grinding stone (or the fixed abrasive), if the polishing cloth is used under a relatively light load such as a finish polishing, then the life of the polishing cloth is prolonged. Further, if the diameter of the polishing cloth is large, the chance or frequency of the contact with the semiconductor wafer is distributed to thus provide a longer life, a longer maintenance period, and an improved productivity of the semiconductor devices.

[0075] After a semiconductor wafer is polished by the first polishing table 34 and before the top ring 32 moves to the second polishing table 35, a cleaning liquid is supplied from cleaning liquid nozzles (not shown) disposed adjacent to the polishing table 34 to the semiconductor wafer held by the top ring 32 at a position where the top ring 32 is spaced from the polishing table 34. Because the semiconductor wafer is rinsed before moving to the second polishing table 35, the transfer of contamination between the polishing tables is prevented to thus avoid cross contamination of the polishing tables.

[0076] Next, as an example of processes for polishing a semiconductor wafer with the polishing apparatus shown in FIG. 1, two cassette parallel processing will be described below.

[0077] That is, one semiconductor wafer is processed in the following route: the wafer cassette 1→the transfer robot 4→the wafer support 7 of the wafer station 48→the transfer robot 20→the reversing device 28→the wafer stage for loading in the rotary transporter 27→the top ring 32→a the polishing table 34→the top ring 32→the wafer stage for unloading in the rotary transporter 27→the reversing device 28→the transfer robot 20→the cleaning apparatus 22→the transfer robot 20→the cleaning apparatus 5→the transfer robot 4→the wafer cassette 1.

[0078] The other semiconductor wafer is processed in the following route: the wafer cassette 1→the transfer robot 4→the wafer support 8 of the wafer station 48→the transfer robot 21→the reversing device 28′→the wafer stage for loading in the rotary transporter 27→the top ring 32→the polishing table 34→the top ring 32→the wafer stage for unloading in the rotary transporter 27→the reversing device 28′→the transfer robot 21→a the cleaning apparatus 23→the transfer robot 21→the cleaning apparatus 6→the transfer robot 4→the wafer cassette 1.

[0079] Next, the detailed structure of the dressing apparatus 50 for dressing the dressing table 35 will be described with reference to FIGS. 3 through 11.

[0080]FIG. 3 is a perspective view showing the polishing table 35 and the dressing apparatus 50. A flat polishing surface 35 a as a polishing tool is formed on an upper surface of the polishing table 35. The dressing apparatus 50 is disposed adjacent to the polishing table 35. The dressing apparatus 50 comprises a dresser 51 for dressing a polishing surface 35 a of the polishing table 35, a dresser arm 52 having a free end for supporting the dresser 51 thereon, and a dresser driving mechanism 53 for swinging the dresser arm 52 and vertically moving the dresser arm 52. The dressing apparatus 50 further comprises a dresser cleaning container 54 for cleaning the dresser 51 by a cleaning liquid stored in the dresser cleaning container 54.

[0081]FIGS. 4, 5A and 5B are views showing the detailed structure of the polishing table 35. FIG. 4 is a vertical cross-sectional view of the polishing table. FIG. 5A is a cross-sectional view taken along line P-P of FIG. 4, and FIG. 5B is a cross-sectional view taken along line X-X of FIG. 5A.

[0082] As shown in FIGS. 4, 5A and 5B, the polishing table 35 has an upper flange 151 of a motor 150, and a hollow shaft 152 connected to the upper flange 151 by bolts. A set ring 154 is supported by the upper portion of the shaft 152 through a bearing 153. A table 159 is fixed to the set ring 154, and the polishing table 35 is fixed to the table 159 by bolts 190. The polishing table 35 may comprise a grinding stone (fixed abrasive) entirely, or may comprise a plate made of a corrosion-resistant metal such as stainless steel and a polishing cloth (polishing pad) attached to the plate. In case of using the grinding stone or the polishing cloth, the polishing table 35 may have a flat upper surface or a slightly convex or concave upper surface. The shape of the upper surface of the polishing table 35 is selected depending on the kind of the semiconductor wafer (substrate) W to be polished. The outer diameter of the polishing table 35 is set to a diameter having the diameter of the semiconductor wafer plus distance 2 e (described below) or larger. That is, the diameter of the polishing table 35 is arranged such a diameter that when the polishing table 35 makes a translational motion, the semiconductor wafer W does not project from the outer periphery of the polishing table 35. The translational motion may be called scroll motion or orbital motion.

[0083] The set ring 154 has three or more supporting portions 158 in a circumferential direction, and the table 159 is supported by the supporting portions 158. A plurality of recesses 160, 161 are formed at positions corresponding to the upper surface of the supporting portions 158 in the set ring 154 and the upper end of a cylindrical member 195 at angularly equal intervals in a circumferential direction, and bearings 162 and 163 are mounted in the recesses 160 and 161. As shown in FIGS. 4, 5A and 5B, a support member 166 having two shafts 164 and 165 whose central axes are spaced by “e” is supported by the bearings 162 and 163. Specifically, the two shafts 164 and 165 are inserted into the bearings 162 and 163, respectively. Thus, the polishing table 35 makes a translational motion along a circle having a radius “e” by the motor 150.

[0084] Further, the center of the shaft 152 is off-centered by “e” from the center of the motor 150. A balancer 167 is fixed to the shaft 152 for providing a balance to the load caused by eccentricity. The supply of the polishing liquid onto the polishing table 35 is conducted through the insides of the motor 150 and the shaft 152, a through-hole 157 provided at the central portion of the table 159, and a coupling 191. The supplied polishing liquid is once stored in a space 156 defined between the polishing table 35 and the table 159, and then supplied to the upper surface of the polishing table 35 through a plurality of through-holes 168 formed in the polishing table 35. The number and position of the through-holes 168 can be selected depending on the kind of processes. In the case where the polishing cloth is attached to the polishing table 35, the polishing cloth has through-holes at positions corresponding to the positions of the through-holes 168. In the case where the polishing table 35 is made of a grinding stone in its entirety, the upper surface of the polishing table 35 has grid-like, spiral, or radial grooves, and the through-holes 168 may communicate with such grooves.

[0085] The supplied polishing liquid may be selected from pure water, chemicals, or slurry, and, if necessary, more than one kind of the polishing liquid can be supplied simultaneously, alternatively, or sequentially. In order to protect a mechanism for performing a translational motion from the polishing liquid during polishing, a flinger or a thrower 169 is attached to the table 159, and forms a labyrinth mechanism together with a trough 170.

[0086] In the polishing table having the above structure, the upper and lower bearings 162, 163 are axially interconnected by the support member 166 comprising a cranked joint having the upper and lower shafts 164, 165 that are fitted respectively in the upper and lower bearings 162, 163. The shafts 164, 165 and hence the upper and lower bearings 162, 163 have respective axes horizontally spaced from each other by a distance “e”. The cylindrical member 195 for supporting the lower bearing 163 is fixed to the frame, and hence is stationary. When the motor 150 is energized, the shaft 152 is rotated by the radius of gyration (e) about the central axis of the motor 150, and thus the polishing table 35 makes a circulatory translational motion (scroll motion) through the cranked joint, and the semiconductor wafer W attached to the top ring 32 is pressed against a polishing surface 35 a of the polishing table 35. The semiconductor wafer W is polished by the polishing liquid supplied through the through-hole 157, the space 156 and the through-holes 168. The semiconductor wafer W is polished by the relative circulatory translational motion having a radius “e” between the polishing surface 35 a of the polishing table 35 and the semiconductor wafer W, and the semiconductor wafer W is uniformly polished over the entire surface of the semiconductor wafer. If a surface, to be polished, of the semiconductor wafer W and the polishing surface have the same positional relationship, then the polished semiconductor wafer is affected by a local difference in the polishing surface. In order to eliminate this influence, the top ring 32 is rotated at a low speed to prevent the semiconductor wafer from being polished at the same area on the polishing surface.

[0087]FIG. 6 is a plan view showing the detailed structure of the dressing apparatus 50. As shown in FIG. 6, the dresser 51 has an elongate shape, and the length l of the dresser 51 is set to be larger than the dimension (corresponding to movement area of the polishing surface) obtained by adding two times eccentricity e″ to the diameter d of the polishing surface 35 a, i.e., l>d+2e. The width of the dresser 51 is set to the dimension as small as possible if the dresser condition permits. That is, when comparing the length l with the diameter d₂ of the semiconductor wafer, l>d₂+4e. This structure of the dresser 51 allows the space in a width direction to be saved greatly, compared with a circular dresser. Similarly, the dresser cleaning container 54 may be rectangular so as to correspond to the shape of the dresser 51, thus saving an installation space of the dresser cleaning container 54. Further, the polishing table does not rotate about its own axis but makes a scroll motion, and therefore the dresser has such a structure that the dresser does not rotate about its own axis. The relative velocity between the polishing table and the dresser becomes equal on every point on the polishing surface by the scroll motion of the polishing table and horizontal movement of the dresser at a constant velocity.

[0088] The dressing apparatus 50 shown in FIG. 6 comprises a cylinder for vertically moving the dresser 51, and a swing mechanism and a link mechanism for horizontally moving the dresser 51. Diamond particles capable of dressing or conditioning the polishing surface are uniformly attached to the entire surface of the dressing surface 51 a of the dresser 51 by electrodeposition or the like. The dressing surface may be composed of ceramics such as SiC (silicon carbide).

[0089]FIGS. 7 and 8 are views showing a configuration of a cross section of an elongate (bar-like) dresser. The dresser 51 shown in FIG. 7 has a substantially rectangular cross section, and a dressing surface 51 a comprises a flat portion (flat surface) 51 a-1, and right and left tapered portions (tapered surfaces) 51 a-2, 51 a-3 disposed at both ends of the flat portion 51 a-1 and inclined upwardly so as to be away from the polishing surface 35 a toward the direction D of movement of the dresser 51. The width of the flat portion 51 a-1 is set to 2 to 5 mm, preferably 3 mm. The angle of inclination of the right and left tapered portions 51 a-2, 51 a-3 is set to 1° to 5°, preferably 2°. The flat portion 51 a-1, and the tapered portions 51 a-2, 51 a-3 comprise electrodeposited diamond surfaces which are formed by electrodepositing diamond particles thereon as shown by bold solid lines. In place of the right and left tapered portions 51 a-2, 51 a-3, these portions may comprise curved surfaces extending from the flat portion 51 a-1 so as to be away from the polishing surface 35 a.

[0090] According to the dresser 51 shown in FIG. 7, a contact area between the dressing surface 51 a of the dresser 51 and the polishing surface 35 a of the polishing table 35 is reduced, and hence a frictional force between the dressing surface and the polishing surface during dressing can be reduced. Thus, vibration of the dresser generated when the dresser 51 reciprocates can be suppressed. Further, since the tapered portions (tapered surfaces) 51 a-2, 51 a-3 inclined upwardly toward the direction of movement of the dresser 51 are formed, edges are not formed at boundary portions between the flat portion (flat surface) 51 a-1 and the tapered portions 51 a-2, 51 a-3, and such boundary portions become smooth. Therefore, a stick-slip caused between the dressing surface and the polishing surface can be decreased, and the dresser 51 can be smoothly moved.

[0091] The dresser 51 shown in FIG. 8 has a substantially rectangular cross section, and the dressing surface 51 a comprises a circular arc surface. The entire surface of the dressing surface 51 a comprises an electrodeposited diamond surface. In the dresser shown in FIG. 8, a contact area between the dressing surface 51 a of the dresser 51 and the polishing surface 35 a of the polishing table 35 can be reduced, as with the dresser shown in FIG. 7. Thus, generation of vibration of the dresser can be suppressed, and the dresser can move smoothly because the dressing surface 51 a comprises a smooth circular arc surface.

[0092] Next, a mechanism for vertically moving the dresser 51 and horizontally moving the dresser 51 in the dressing apparatus 50 will be described with reference to FIGS. 9 through 11.

[0093] As shown in FIGS. 9 through 11, the dressing apparatus 50 comprises a vertical shaft 58 which moves vertically and is guided by a linear guide 56 fixed to a base 55, a swing shaft 60 having a follow structure and enclosing the vertical shaft 58, and a dresser arm 52 coupled to the swing shaft 60. The dresser arm 52 has a free end which supports the dresser 51. On the other hand, a lifting/lowering cylinder 62 is fixed to the base 55, and has a piston rod whose upper end is coupled to a lifting/lowering base 64 fixed to the vertical shaft 58. The lifting/lowering base 64 is fixed to the vertical shaft 58.

[0094] The vertical shaft 58 has an upper end to which a drive pulley 68 is mounted, and a belt 74 is provided between the drive pulley 68 and a driven pulley 72 mounted on a dresser support shaft 70 rotatably provided at the free end of the dresser arm 52. A bearing 71 is interposed between the vertical shaft 58 and the swing shaft 60. Further, the dresser support shaft 70 extends downwardly, and has a lower end to which the dresser 51 is attached.

[0095] On the other hand, a swing cylinder 76 is fixed to the lifting/lowering base 64, and a piston rod of the swing cylinder 76 is connected through a ball joint 80 to a forward end of a link arm 78 projecting in a direction perpendicular to an axis of the swing shaft 60. Thus, when the lifting/lowering cylinder 62 is actuated, the swing cylinder 76 is vertically moved integrally with the lifting/lowering base 64, and when the swing cylinder 76 is actuated, the swing shaft 60 is rotated to allow the dresser arm 52 to be swung. When the dresser arm 52 is swung, the dresser 51 moves horizontally to perform a translation at a constant speed in one direction by a translation mechanism comprising the pulleys 68, 72 and the belt 74.

[0096] In this embodiment, the dresser cleaning container 54 serves to prevent the dressing surface 51 a of the dresser 51 from drying. As shown in FIG. 10, a tube 82 is attached to the dresser cleaning container 54 for supplying a cleaning liquid to the dresser cleaning container 54, and the cleaning liquid is always supplied to the dresser cleaning container 54 to keep the cleaning liquid in the dresser cleaning container 54 clean. The dresser 51 is located at a lowered position on the standby condition, and the dressing surface 51 a is immersed in the cleaning liquid in the dresser cleaning container 54 to prevent the dressing surface 51 a from drying.

[0097] Next, a series of operations in which the dresser 51 is removed from the dresser cleaning container 54, and dresses the polishing surface 35 a of the polishing table 35, and then returned to the dresser cleaning container 54 will be described.

[0098] The dresser 51 is located at a lowered position in the dresser cleaning container 54. By actuating the lifting/lowering cylinder 62, the dresser 51 is lifted and removed from the dresser cleaning container 54. The lifting position of the dresser 51 is determined by the stopper 66. In this state, the swing cylinder 76 is actuated, and the swing shaft 60 is rotated to swing the dresser arm 52 toward the polishing surface 35 a of the polishing table 35. Then, since the drive pulley 68, the driven pulley 72 and the belt 74 jointly constitute a link mechanism for performing a translation of the dresser 51, even if the dresser arm 52 is swung by rotation of the swing shaft 60, the dresser 51 does not change its direction but performs a translation. Therefore, the dresser 51 is transferred onto the polishing surface 35 a of the polishing table 35, and then the dressing surface 51 a is pressed against the polishing surface 35 a to dress the polishing surface 35 a by the dressing surface 51 a. The center of the dresser 51 passes through the center of the polishing surface 35 a, and the length 1 of the dresser 51 is larger than the diameter of the circle which is described by the outer periphery of the polishing surface 35 a which makes a scroll motion. Thus, the dresser 51 can dress the entire area of the polishing surface 35 a.

[0099] The dresser 51 moves along the polishing surface 35 a while dressing the polishing surface 35 a which makes a scroll motion, and reaches an end of the polishing surface 35 a at its stroke end and stops. Thereafter, the dresser 51 moves in an opposite direction by switching the operational direction of the link mechanism while dressing the polishing surface 35 a. As shown in FIG. 9, a sensor 84 for detecting the stroke end of the swing cylinder 76 is attached to the swing cylinder 76 to determine timing of switching the direction of the link mechanism and monitor the operation.

[0100] The dressing is repeated by the predetermined number of times, and then the dresser is returned to the dresser cleaning container 54 and dressing operation is terminated.

[0101] In the dressing apparatus 50 of the present invention, a device for controlling a pressing force for pressing the dressing surface 51 a of the dresser 51 against the polishing surface 35 a is used. Specifically, as shown in FIG. 11, the lifting/lowering cylinder 62 is used as a lifting/lowering mechanism of the dresser 51, and air pressure supplied to the lifting/lowering cylinder 62 is controlled by a controller 63 such as an electropneumatic regulator so that the difference (Wt-F) between a weight Wt of the mechanism and a thrust F of the lifting/lowering cylinder 62 becomes a target pressing force for pressing the dresser 51 against the polishing surface 35 a.

[0102]FIGS. 12A and 12B are views showing a method for controlling a pressing force for pressing the dressing surface 51 a against the polishing surface by using the method for controlling the pressing force of the dresser shown in FIG. 11. FIG. 12A is a schematic view showing the relationship between the polishing table and the dresser, and FIG. 12B is a graph showing the relationship between the distance from the center of the polishing table, and a pressing force and a pressure of the dresser.

[0103] As shown in FIG. 12A, as the dresser 51 moves radially outwardly from the center O of the polishing table 35, a contact area between the dressing surface 51 a of the dresser 51 and the polishing surface 35 a of the polishing table 35 decreases. Therefore, if a pressing force (a pressing force applied to the entire dressing surface) of the dresser 51 is constant, a pressing force (a pressure applied to the polishing surface per unit area) is not constant, thus suffering a change of an amount of a material removed from the polishing surface.

[0104] Therefore, in the present embodiment, as shown in FIG. 12B, as the dresser 51 moves radially outwardly from the center O of the polishing table 35, the pressing force (Wt-F: a pressing force applied to the entire dressing surface) of the dresser 51 is controlled so as to be smaller by the controller 63. Thus, irrespective of the position of the dresser, the pressing force P (a pressure applied to the polishing surface per unit area) is controlled so as to be constant, and hence an amount of material removed from the polishing surface becomes constant. In this case, if horizontal movement of the dresser 51 is performed by a pulse motor, the position of the dresser 51 is determined by the number of pulses in the pulse motor, and if the pressure of the lifting/lowering cylinder 62 is controlled according to the position of the dresser 51 by the controller 63, then the pressing force (Wt-F) of the dresser 51 can be controlled according to the position of the dresser 51. The lifting/lowering cylinder 62 may be replaced with an electric actuator such as a linear stepping motor, and the controller 63 may be an electric circuit.

[0105]FIG. 13 is a plan view of a polishing table according to another embodiment of the present invention. In the embodiment shown in FIG. 13, the polishing table 35 is substantially rectangular. Specifically, both side ends 35 s, 35 s of the polishing table 35 are formed linearly in parallel to each other, and upper and lower ends 35 e, 35 e are formed arcuately in parallel to each other. The length l of the dresser 51 is longer than the length d of the polishing table 35. The upper and lower ends 35 e, 35 e of the polishing table 35 are located inwardly of circular arc loci described by the upper and lower ends of the dresser 51. The both side ends 35 s, 35 s of the polishing table 35 are located outwardly of the moving area of the dresser 51. That is, the dresser 51 performs a dressing operation within the both ends of the polishing table 35 which makes a scroll motion so that the dresser 51 does not fall out of the polishing table 35. In the embodiment shown in FIG. 12, the polishing table is circular, and hence the pressing force of the dresser is changed according to the position of the dresser. However, in the embodiment shown in FIG. 13, a contact area between the dressing surface of the dresser 51 and the polishing surface 35 a of the polishing table 35 is always constant irrespective of the position of the dresser, and hence the pressing force of the dresser is not changed and is always constant.

[0106] Next, a linear polishing apparatus having a dressing apparatus according to the present invention will be described below with reference to FIGS. 14A, 14B and 15.

[0107]FIGS. 14A and 14B are views of a linear polishing apparatus, and FIG. 14A is a plan view of the linear polishing apparatus and FIG. 14B is a front view of the linear polishing apparatus. FIG. 15 is a perspective view of the linear polishing apparatus shown in FIGS. 14A and 14B. In the linear polishing apparatus, a polishing table 212 which reciprocates linearly in a horizontal direction is placed on a guide surface of a guide rail 211 serving as a linear guide whose guide surface is disposed horizontally.

[0108] Here, x, y, and z are rectangular coordinates defining a position of a point in space. In this case, x-axis is in a direction of a reciprocating linear motion along the guide rail 211, y-axis is in a direction perpendicular to the x-axis and is in a horizontal plane, and z-axis is in a vertical direction. A first direction of the present invention corresponds to a direction of x-axis.

[0109] The upper surface of the polishing table 212 constitutes a polishing surface 213 contained in a horizontal plane. The polishing surface 213 is divided into a rough polishing surface 214 for rough polishing and a fine polishing surface 215 for finish polishing. Between the rough polishing surface 214 and the fine polishing surface 215, there is provided a multifunction groove 216 formed linearly in a direction (y-axis direction) perpendicular to the direction of the linear motion (x-axis direction) along the guide rail 211. In the following description, if it is not necessary to distinguish between the rough polishing surface 214 and the fine polishing surface 215, the polishing surface is simply referred to as the polishing surface 213.

[0110] In this embodiment, although the polishing surface includes two kinds of the polishing surfaces 214 and 215, the polishing surface may include three or more kinds of polishing surfaces depending on a process. For example, in addition to the rough polishing surface and the fine polishing surface, there may be provided a reforming surface for reforming a surface of a substrate for the purpose of improving a cleaning effect of the substrate. A thick disk-like top ring 217 for holding a substrate W such as a semiconductor wafer to be polished and pressing the substrate W against the polishing surface 213 is provided above the polishing surface 213. The top ring 217 is connected at an opposite side of the holding surface of the substrate W to a pressing mechanism 218 for rotating the top ring 217 about a vertical axis and pressing the top ring 217. The pressing mechanism 218 serves to move the top ring 217 in a horizontal direction perpendicular to the moving direction of the polishing table 212, and also to press the top ring 217 against the polishing surface 213. The pressing mechanism 218 is adapted to be moved by an arm 219 (see FIG. 15).

[0111] Further, two elongate rectangular dressers 221 a, 221 b for dressing the polishing surface 213 are disposed adjacent to the top ring 217 in the x-axis direction. The two dressers 221 a, 221 b are located at positions which are symmetrical with respect to the top ring 217. The dressers 221 a, 221 b have respective dressing surfaces 222 a, 222 b which confront the polishing surface 213. The dressers 221 a, 221 b are elongate and have a rectangular cross section, and the dressing surfaces 222 a, 222 b are rectangular and a longitudinal direction of each of the rectangular dressing surfaces 222 a, 222 b corresponds to the y-axis direction. Further, nozzles 223 a, 223 b for supplying liquid to the respective dressers 221 a, 221 b are provided between the top ring 217 and the dressers 221 a, 221 b, respectively. Further, rectangular dresser cleaning containers 224 a, 224 b are disposed at the opposite sides of the respective nozzles 223 a, 223 b in the x-axis direction with respect to the respective dressers 221 a, 221 b, and a longitudinal direction of each of the rectangular dresser cleaning containers 224 a, 224 b corresponds to the y-axis direction. In the following description, in the case where a plurality of identical elements, for example, two identical elements such as the dressers 221 a, 221 b are not necessary to be distinguished from each other, suffix a, b are omitted, and they are simply referred to as, for example, the dresser 221.

[0112] Next, operation of the linear polishing apparatus having the above structure will be described with reference to FIGS. 14A, 14B and 15.

[0113] When a polishing process is started, the substrate W held by the top ring 217 under vacuum with a surface, to be polished, of the substrate W facing downwardly is pressed against the polishing surfaces 214, 215 which reciprocate linearly in the x-axis direction.

[0114] The top ring 217 reciprocates linearly in the direction (y-axis direction, a third direction of the present invention) perpendicular to the direction (x-axis direction) of the reciprocating linear motion of the polishing surfaces 214, 215. In order to prevent a polished surface of the substrate from being scratched locally, the top ring 217 is rotated at a low rotational speed such as about 10 min⁻¹. Because the rotational speed of the top ring 217 is low, the surface, to be polished, of the substrate W substantially makes a linear motion with respect to the polishing surface 213. In other words, the top ring 217 is rotated at such a low speed as to allow the surface, to be polished, of the substrate to make a linear motion substantially with respect to the polishing surface 213.

[0115] In general, the surface, to be polished, of the substrate which is stationary and is pressed against the polishing surface 213 which makes a reciprocating linear motion has the same moving speed with respect to the polishing surface at every point on the entire surface of the substrate, and hence uniform polishing can be performed theoretically over the entire surface of the substrate. Further, in this embodiment, by rotating the substrate at a very low speed, uniform polishing of the surface of the substrate can be performed, and a polished surface of the substrate can be prevented from being scratched or damaged locally.

[0116] A plurality of holes (not shown) for discharging a polishing liquid are formed in the polishing surfaces 214, 215 to supply the polishing liquid therethrough directly between the polishing surfaces 214, 215 and the substrate W. Because the polishing liquid is supplied in this manner, although slurry such as a polishing liquid is difficult to be supplied in the reciprocating linear motion differently from the rotating motion, the polishing liquid can be uniformly supplied over the entire surface, to be polished, of the substrate.

[0117] First, in order to perform a rough polishing of the substrate W by the polishing surface 214, the polishing table 212 makes a reciprocating linear motion in the x-axis direction to polish the substrate W only by the polishing surface 214. Similarly, in case of finish-polishing of the substrate by the polishing surface 215, the polishing table 212 makes a reciprocating linear motion in the x-axis direction within the area of the polishing surface 215. In this manner, polishing of different roughness can be performed on the same polishing table 212.

[0118] The polishing surfaces 214, 215 may comprise an elastic pad such as a polishing cloth. Because the polishing table 212 has such a structure that the polishing table 212 makes a reciprocating linear motion, at least one of the polishing surfaces 214, 215 may comprise a fixed abrasive (abrading plate). If the fixed abrasive is used, formation of dishing in the polished surface of the substrate can be prevented. Since the polishing table 212 makes a reciprocating linear motion, the upper surface of the polishing table 212 is normally a rectangular surface having a certain area differently from the endless belt, thus facilitating replacement of the elastic pad or the fixed abrasive.

[0119] To be more specific, in the polishing apparatus in which a polishing surface is formed by attaching a polishing pad, a polishing liquid is supplied between a substrate and a polishing pad. However, since the polishing pad is an elastic body, even if the substrate is polished by applying a pressure uniformly over the entire surface of the substrate, in the substrate whose surface to be polished has irregularities, not only raised regions but also depressed regions are polished. Therefore, when polishing of the raised regions is completed, polishing of the depressed regions makes progress inevitably, and such depressed regions formed after polishing are called “dishing”. In order to increase the polishing rate, it is conservable to increase the pressing force for pressing the substrate against the polishing surface. However, if the polishing pad is used as a polishing surface, then the above-mentioned problem arises remarkably, and hence it is difficult to cope with both high polishing rate and high planarization.

[0120] However, as in the embodiment of the present invention, if the fixed abrasive (abrading plate) is used, both high polishing rate and prevention of forming of dishing are compatible. Specifically, the fixed abrasive (abrading plate) is suitable for the polishing surface 214 for rough polishing. In either case of the polishing surface 214 for rough polishing and the polishing surface 215 for finish polishing, it is suitable to provide a groove so as to extend fully across the polishing surface. The groove preferably extends at a right angle to the moving direction (x-axis direction) of the polishing surface, or extends obliquely for promoting a discharge of the used polishing liquid or the like or preventing peeling of the polishing pad.

[0121] Further, in order to perform polishing of the workpiece (substrate) at high efficiency, there are some cases where two kinds of polishing, i.e. rough polishing and finish polishing are required in one stroke. Conventionally, because these polishing surfaces are separately provided at different positions, the necessity of various kinds of polishing surfaces leads to an increase of an installation area of the apparatuses. However, in the embodiment of the present invention, a plurality of polishing surfaces including a polishing surface for rough polishing and a polishing surface for finish polishing, for example, two kinds of polishing surfaces 214, 215 are prepared as a polishing surface 213, and hence it is possible to provide a polishing apparatus which can polish workpieces at high efficiency, without increasing an installation area of the apparatus.

[0122] Thus, the polishing table 212 is provided with a fixed abrasive and a polishing cloth selectively, and a workpiece can be polished on the condition suitable for a shape or property of a surface, to be polished, of the workpiece (substrate), thus improving polishing precision of the workpiece. Further, by providing two or more polishing surfaces having the same property or different property on a single polishing table, a processing capability per unit installation area can be increased, and the degree of freedom for constructing a polishing process can be heightened.

[0123] Next, a dressing process for dressing the polishing surfaces 214, 215, removing foreign materials from the polishing surfaces 214, 215 and regenerating the polishing surfaces 214, 215 will be described below. The dressing surfaces 222 a, 222 b of the dressers 221 a, 221 b are pressed against the polishing surfaces 214, 215 which make a reciprocating linear motion in the x-axis direction. The dressing surfaces 222 a, 222 b comprise an electrodeposited diamond surface. These dressing surfaces have the same structure as those shown in FIGS. 7 and 8.

[0124] The dressers 221 a, 221 b reciprocate linearly in the direction (y-axis direction, a second direction of the present invention) perpendicular to the moving direction of the polishing surfaces 214, 215 (x-axis direction). In this manner, by providing the dressers 221 a, 221 b which move in the direction perpendicular to the polishing surfaces 214, 215 which reciprocate linearly, the entire polishing surfaces 214, 215 can be uniformly dressed. When dressing of the polishing surfaces 214, 215 are carried out, a dressing liquid is discharged from the nozzles 223 a, 223 b provided in the vicinity of the dressers 221 a, 221 b to discharge foreign materials on the polishing surfaces 214, 215 to the outside of the polishing surfaces 214, 215. By providing the dressers 221 a, 221 b on both sides of the top ring 217, the distance of reciprocating linear motion of the dressers 221 a, 221 b in the x-axis direction at the time of dressing can be shortened, and the dressing apparatus can be downsized. The rectangular dressers 221 a, 221 b preferably have such a size that the length of the dressing surfaces 222 a, 222 b in the longitudinal direction is longer than the width of the polishing table 212. With this structure, uniformity of the dressing can be improved.

[0125] If foreign materials are accumulated at positions near the top ring 217, such foreign materials have a bad influence on polishing performance. Therefore, for example, in the latter half of the dressing process, when the ends of the polishing table 212 are moving apart from the dressers 221 a, 221 b, the dressers 221 a, 221 b are moving so as to be away from the polishing surfaces 214, 215. Conversely, when the ends of the polishing table 212 are moving toward the dressers 221 a, 221 b, the dressers 221 a, 221 b are brought into contact with the polishing surfaces 214, 215 to sweep foreign materials or the like out of the polishing table 212 in the direction opposite to the multifunction groove 216. In this case, the polishing table 212 moves up to a position where the dressers 221 a, 221 b are brought out of contact with the polishing table 212, thereby completely sweeping foreign materials or the like out of the polishing table 212. Further, foreign materials or the like collected by the dressers 221 a, 221 b may be discharged by using discharge function of the multifunction groove 216.

[0126] In the case where dressing is not carried out, the dressers 221 a, 221 b are on standby at positions away from the polishing surfaces 214, 215 by using the lifting/lowering mechanism, and the discharge positions of the nozzles 223 a, 223 b are determined so that the dressing surfaces 222 a, 222 b can be rinsed at these positions also by liquid supplied from the nozzles 223 a, 223 b.

[0127] In the above embodiment, the elongate (bar-like) dressers 221 a, 221 b are disposed such that the longitudinal direction of each of the dressers 221 a, 221 b corresponds to the y-axis direction, and the direction of reciprocating linear motion of the dressers 221 a, 221 b corresponds to the y-axis direction as a second direction. However, the arrangement of the dressers 221 a, 221 b is not limited to the above arrangement, and it may be sufficient to allow the direction of reciprocating linear motion of the dressers 221 a, 221 b to be across the x-axis direction. The second direction is preferably in the same direction as the multifunction groove 216. Similarly, as the third direction, the direction of reciprocating linear motion of top ring 217 corresponds to the y-axis direction. However, the direction of reciprocating linear motion of the top ring 217 is not limited to this direction, and it may be sufficient to allow such direction to be across the x-axis direction.

[0128]FIGS. 16A and 16B are views showing a dressing apparatus and a polishing apparatus having such dressing apparatus according to still another embodiment of the present invention. FIG. 16A is a plan view of the polishing apparatus, and FIG. 16B is a side view of the polishing apparatus. In this embodiment, a polishing table 300 comprises a rotating type turntable which rotates about its own axis O. A polishing surface 300 a comprising an abrading plate (fixed abrasive) or a polishing cloth is provided on the upper surface of the polishing table 300. A dresser 310 is connected to an air cylinder (not shown) and is movable vertically. During dressing, the polishing table 300 rotates about its own axis, and hence the dresser 310 is not required to be moved horizontally and is stationary in the state shown in FIG. 16A. Therefore, if the standby position of the dresser 310 is located above the polishing table 300, then a mechanism for moving the dresser 310 horizontally is not necessary. The dressing surface 310 a of dresser 310 has the same structure as those shown in FIGS. 7 and 8. In this embodiment also, the dresser offers the same advantages as those shown in FIGS. 7 and 8.

[0129] As described above, the present invention offers the following advantages:

[0130] (1) During dressing, a frictional force between the dressing surface and the polishing surface can be reduced. Therefore, when the dresser reciprocates, generation of vibration of the dresser can be suppressed. Further, because the boundary portion between a contact portion and a noncontact portion of the dressing surface and the polishing surface has a smooth shape, the dresser can be smoothly moved on the polishing surface.

[0131] (2) Because the size of the dressing surface in the long side has the dimension larger than that of the moving area of the polishing surface of the polishing table, and the dresser is movable along the polishing surface by a horizontally moving mechanism, the entire area of the polishing surface can be dressed by bringing the dressing surface in contact with the polishing surface and moving the dressing surface. Therefore, even if the polishing surface has irregularities locally, the entire area of the polishing surface can be reliably planalized, and the polishing surface can be efficiently and uniformly regenerated.

[0132] (3) The polishing table which makes a scroll motion and has an advantage of space-saving can be reliably dressed by the dresser requiring a small installation area, and hence processing capability per unit installation area of the polishing table can be improved.

[0133] (4) In the case where a contact area between the dressing surface and the polishing surface is changed by relative movement between the dresser and the polishing table during dressing, a pressing force of the dresser applied to the polishing table (pressing force applied to the entire dressing surface) is changed according to the contact area, and hence a pressing force for pressing the dressing surface against the polishing surface (pressure applied to the polishing surface per unit area) can be equalized over the entire polishing surface. Thus, an amount of a material removed from the polishing surface on the polishing table can be uniformized over the entire polishing surface.

[0134] (5) Inasmuch as a contact area between the dressing surface of the dresser and the polishing surface is not changed over the entire area where the dresser moves, a pressing force for pressing the dresser against the polishing surface can be constant, irrespective of the position of the dresser.

[0135] Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.

[0136] The present application is based on the Japanese Priority Patent Application No. 2000-350820, filed Nov. 17, 2000, and the entire disclosure of which is hereby incorporated by reference. 

What is claimed is:
 1. A dressing apparatus for dressing a polishing surface of a polishing table for polishing a surface of a workpiece, the dressing apparatus comprising: a dresser having an elongate dressing surface for dressing said polishing surface, said dressing surface having a flat surface which contacts said polishing surface, and one of a tapered surface extending from said flat surface and inclined so as to be away from said polishing surface and a curved surface extending from said flat surface and curved so as to be away from said polishing surface.
 2. A dressing apparatus according to claim 1, wherein said dressing surface of said dresser has a dimension in the long side which is longer than a dimension of a moving area of said polishing surface, said moving area of said polishing surface is used for polishing, and said dresser is movable along said polishing surface by a moving mechanism.
 3. A dressing apparatus according to claim 1, wherein a material for forming said dressing surface comprises one of diamond particles and ceramics.
 4. A dressing apparatus according to claim 1, wherein said dresser performs no rotational motion about its own axis during dressing.
 5. A dressing apparatus according to claim 1, further comprising a dresser cleaning container for cleaning said dressing surface of said dresser.
 6. A dressing apparatus for dressing a polishing surface of a polishing table for polishing a surface of a workpiece, the dressing apparatus comprising: a dresser having an elongate dressing surface for dressing said polishing surface, said dressing surface comprising a circular arc surface.
 7. A dressing apparatus according to claim 6, wherein said dressing surface of said dresser has a dimension in the long side which is longer than a dimension of a moving area of said polishing surface, said moving area of said polishing surface is used for polishing, and said dresser is movable along said polishing surface by a horizontally moving mechanism.
 8. A dressing apparatus according to claim 6, wherein a material for forming said dressing surface comprises one of diamond particles and ceramics.
 9. A dressing apparatus according to claim 6, wherein said dresser performs no rotational motion about its own axis during dressing.
 10. A dressing apparatus according to claim 6, further comprising a dresser cleaning container for cleaning said dressing surface of said dresser.
 11. A dressing apparatus for dressing a polishing surface of a polishing table for polishing a surface of a workpiece, the dressing apparatus comprising: a dresser having a dressing surface for dressing said polishing surface, said dressing surface having a flat surface which contacts said polishing surface, and one of a tapered surface extending from said flat surface and inclined so as to be away from said polishing surface and a curved surface extending from said flat surface and curved so as to be away from said polishing surface; wherein said dresser performs no rotational motion about its own axis during dressing.
 12. A dressing apparatus according to claim 11, wherein said dressing surface of said dresser has a dimension in the long side which is longer than a dimension of a moving area of said polishing surface, said moving area of said polishing surface is used for polishing, and said dresser is movable along said polishing surface by a moving mechanism.
 13. A dressing apparatus according to claim 11, wherein a material for forming said dressing surface comprises one of diamond particles and ceramics.
 14. A dressing apparatus according to claim 11, further comprising a dresser cleaning container for cleaning said dressing surface of said dresser.
 15. A dressing apparatus for dressing a polishing surface of a polishing table for polishing a surface of a workpiece, the dressing apparatus comprising: a dresser having a dressing surface for dressing said polishing surface, said dressing surface comprising a circular arc surface; wherein said dresser performs no rotational motion about its own axis during dressing.
 16. A dressing apparatus according to claim 15, wherein said dressing surface of said dresser has a dimension in the long side which is longer than a dimension of a moving area of said polishing surface, said moving area of said polishing surface is used for polishing, and said dresser is movable along said polishing surface by a horizontally moving mechanism.
 17. A dressing apparatus according to claim 15, wherein a material for forming said dressing surface comprises one of diamond particles and ceramics.
 18. A dressing apparatus according to claim 15, further comprising a dresser cleaning container for cleaning said dressing surface of said dresser.
 19. A dressing apparatus for dressing a polishing surface of a polishing table for polishing a surface of a workpiece, the dressing apparatus comprising: a dresser having a dressing surface for dressing said polishing surface; and a controller for controlling a pressing force for pressing said dresser against said polishing surface; wherein when a contact area between said dressing surface of said dresser and said polishing surface is changed by relative movement of said dresser and said polishing table during dressing, said pressure force is changed according to said contact area by said controller.
 20. A dressing apparatus according to claim 19, further comprising a dresser cleaning container for cleaning said dressing surface of said dresser.
 21. A polishing apparatus for polishing a surface of a workpiece, the polishing apparatus comprising: a polishing table having a polishing surface; and a dresser having a dressing surface for dressing said polishing surface, said dresser being movable along said polishing surface by a moving mechanism; wherein a shape of said polishing surface is arranged such that a contact area between said dressing surface of said dresser and said polishing surface is not changed when said dresser is moved by said moving mechanism.
 22. A polishing apparatus according to claim 21, further comprising a dresser cleaning container for cleaning said dressing surface of said dresser.
 23. A polishing apparatus for polishing a surface of a workpiece, comprising: a polishing table having a polishing surface; a workpiece holder for holding a workpiece; a pressing device for pressing the workpiece held by said workpiece holder against said polishing surface; and a dressing apparatus for dressing said polishing surface, the dressing apparatus comprising: a dresser having an elongate dressing surface for dressing said polishing surface, said dressing surface having a flat surface which contacts said polishing surface, and one of a tapered surface extending from said flat surface and inclined so as to be away from said polishing surface and a curved surface extending from said flat surface and curved so as to be away from said polishing surface.
 24. A polishing apparatus for polishing a surface of a workpiece, comprising: a polishing table having a polishing surface; a workpiece holder for holding a workpiece; a pressing device for pressing the workpiece held by said workpiece holder against said polishing surface; and a dressing apparatus for dressing said polishing surface, the dressing apparatus comprising: a dresser having an elongate dressing surface for dressing said polishing surface, said dressing surface comprising a circular arc surface.
 25. A polishing apparatus for polishing a surface of a workpiece, comprising: a polishing table having a polishing surface; a workpiece holder for holding a workpiece; a pressing device for pressing the workpiece held by said workpiece holder against said polishing surface; and a dressing apparatus for dressing said polishing surface, the dressing apparatus comprising: a dresser having a dressing surface for dressing said polishing surface, said dressing surface having a flat surface which contacts said polishing surface, and one of a tapered surface extending from said flat surface and inclined so as to be away from said polishing surface and a curved surface extending from said flat surface and curved so as to be away from said polishing surface; wherein said dresser performs no rotational motion about its own axis during dressing.
 26. A polishing apparatus for polishing a surface of a workpiece, comprising: a polishing table having a polishing surface; a workpiece holder for holding a workpiece; a pressing device for pressing the workpiece held by said workpiece holder against said polishing surface; and a dressing apparatus for dressing said polishing surface, the dressing apparatus comprising: a dresser having a dressing surface for dressing said polishing surface, said dressing surface comprising a circular arc surface; wherein said dresser performs no rotational motion about its own axis during dressing.
 27. A polishing apparatus for polishing a surface of a workpiece, comprising: a polishing table having a polishing surface; a workpiece holder for holding a workpiece; a pressing device for pressing the workpiece held by said workpiece holder against said polishing surface; and a dressing apparatus for dressing said polishing surface, the dressing apparatus comprising: a dresser having a dressing surface for dressing said polishing surface; and a controller for controlling a pressing force for pressing said dresser against said polishing surface; wherein when a contact area between said dressing surface of said dresser and said polishing surface is changed by relative movement of said dresser and said polishing table during dressing, said pressure force is changed according to said contact area by said controller. 